Method of and apparatus for drying and enameling



Aug. 9, 1927.

, A. MAEHLER ET AL METI-I OD OF AND APPARATUS FOR DRYING AND ENAMELINGIIII //v v/v TORS. #Z VEHLE/7&/(A RL 157565.15,

M ATTORNEY.

I l l I I l I I I l I l I I I I l I l l I I l l I II Aug. 9 1927.

A. MAEHLER ET AL METHOD or AND APPARATUS FOR DRYING AND'ENAMELING FiledAu 5, 1926 4 Sheets-Sheet 2 5 MA TTORNEY.

' Aug. 9,1927. 1,638,811

A. MAEHLER ET AL METHOD OF AND APPARATUS FOR DRYING AND nmusmue Filed Au5, 1926 4 Sheets-Sheet 3 A TTORNEY.

1,638,811 1927' A. MAEHLER ET AL mmron OF AND APPARATUS FOR DRYING ANDENAMELING Filed Auz. 5, 1926 4 Sheets-Sheet '4 A TTORNE Y.

the operation of the same,

Patented Aug. 9, 1927.

UNITED STATES PATENT OFFICE.

ARTHUR MAEHLER AND KARL SIEGELE, OF CHICAGO, ILLINOIS; SAID SIEGELEASSIGNOR T SAID MAEHLEB.

METHOD OF AND APPARATUS FOR DRYING AND ENAMELING.

Application filed August 5, 1926. Serial No. 127,276.

This invention relates to that type of drying or enameling methods andapparatus 1n which the volatile constituents or solvents of anon-vitreous enamel coating are removed 5 by the combined action of heatand a normal and continued draft or circulation of air through the ovenchamber, and discharged at a point outside such oven chamber. In suchmethod and during the initial period in for instance the first twentyminutes, the main portion of the volatile constituents of the enamelingcoating are driven off as vapor into the oven chamber.

notsufiicient to properly carry off orreduce the proportion of suchvolatile and explosive vapor in the aeriform contents of the ovenchamber, accidental and destructive explosions within the oven chamberare of frequent occurrence with material damage to the oven structureand adjoining portions of the building. With a view to remove suchdanger and liability to explosions within the oven chamber, the presentimprovements have for their main objects:

To provide means and a method of control. whereby a supply of heated airis forced through the oven chamber for a predetermined period of timeand during the initial operation of the oven in order to attain a safeand effective dilution and removal of the excessive amount of explosivegaseous vapor given off by the enamel coating in the initial portion ofthe enameling or drying operation.

Another object of the improvement is to provide an automatic operativeinter-connection of the motor of the pressure. blower by which thesurplus supply of air, above referred to, is forced through the ovenchamher, with the oven door or doors, so that the motor. will berendered operative only when both the entry and exit doors are in theirclosed condition, when such operative condition of the motor is attainedwith the closing of the last one of said doors.

Still anther object of the improvement, is to provide a time controlledswitch mecha- In that the normal draft or cir- I 15 culation of airthrough the oven chamber is nism, interconnected with the motor and themotor controlled door means, in order to automatically render said motorinoperative 1n a predetermined period of time after the normal startingof said motor in the initial portion of the present drying or enamelingoperation, all as will hereinafter more fully appear.

In the accompanying drawings:

Fig. 1, is a plan view of a drying and enameling oven having the presentimprovement applied and showing the electrically actuated and controlledtype of the invention.

Fig. 2, is a longitudinal section on line 22 ,Fig. 1.

Fig. 3, is a transverse section on line 33, Fig. 2.

Fig. 4, is a detail sectional plan of the door switches, the time switchand its operating mechanism in their associated relations.

Figs. 5 and 6, are detail sectional plan views, showing other relativepositions of the time and the door switch mechanisms.

Like reference numerals indicate like parts in the several views.

The means shown in the drawings to illustrate the present invention isthe ordinary rectangular and indirectly heated type of oven, preferablyof that form having a middle wall or partition 1 extending the length ofthe oven structure and intermediate of 8 the side walls 2 and 3 thereof,to divide the interior of the structure into a pair of oven chambersprovided with entry and exit doorways in the front and rear walls of theoven structure, and with said doorways closed by 8 doors 4 and 5, asshown.

The indirect heating means for each oven chamber consists of the usualpair of opposed heating units located along the sides of the ovenchamber, and with each of said units comprising a lower horizontal trunk6, the chamber of which contains the heating means, either electrical orthe ordinary gas burner 7 shown in Fig. 4, and a plurality of verticalmains or headers 8, extending up 05 from the trunk 6 and connectedtogether by tubular members 9, with the parts coacting to perform thedesired indirect heating function of an oven chamber. In the construction shown, the central one of the headers 8 extends up through theoven roof and may have communication with the usual outlet or uptakestack of the oven.

In the ventilating means shown, the supply of outer air enters intaketrunks 10 arranged horizontally in the over chambers, between therespective side and middle walls, 1, 2 and 3, and adjacent heatingunits, and at about the mid-height of the oven chambers, as shown inFigs. 2 and 3. At the midlength of the. oven, each of said intake trunks 1U communicate with a vertical conduit 11 which in turn communicateswith an outlet header 12 arranged longitudinally in the upper portion ofan oven chamber, and having an opening or slot along its length for thepassage of air in the upper portion of the oven chamber.

The associated means for eflecting an efiicient ventilating circulationof the air through the oven chambers involves an exhaust'fan or airmover 13, usually located on the roof of the oven structure, with itssuction or intake trunk having dual connections as follows: With theupper portion of each chamber by a conduit 14 extending to a centrallongitudinally arranged vent duct 15 in said top portion of the ovenchamber, and with the lower portion of each oven chamber through acentral opening 16 in the floor thereof, and through conduits 17,extending to and communicating with the suction or intake trunk of theexhaust fan 13 aforesaid.

The means above described for heating and ventilating the oven chambersformsno material part of the present invention other than showing apractical and eflicient ventilating and indirect heating means for usein connection with the present invention.

A novel andmaterial portion of the present invention consists in the useof a rotary pressure blower 18, which in the construction shown in thedrawings has communication in common with the two oven chambers of thestructure by means of a plurality of conduits arranged as follows Acentral conduit 19 extending downwardly from the pressure outlet trunkof the blower 18, preferably at the outside of the oven structure, anddischarging into the hereinafter described pair of conduits by which airfrom the blower 18 is heated and discharged into the upper portions ofthe oven chambers adjacent to the partition wall 3, separating said ovenchambers. And a pair of side conduits 20, also extending downwardly fromthe pressure outlet trunk of the blower 18, preferably at the outside ofthe oven structure, and discharging into the hereinafter describedconduits by which air from said blower is heated and dis charged intothe respective upper portions of the oven chambers adjacent to the sidesof the same.

The plurality of conduits within the oven structure, above referred to,are a counterpart construction, and each of said conduits preferablycomprises a detail construction as follows:

A horizontal. trunk 21 arranged in a lower corner of an oven chamber andhaving communication at one end with the outlet trunk of the pressureblower 18 through. one or the other of the intermediate conduits 19, 20,aforesaid. Near to its other end the trunk 21 is divided by a horizontalpartition 22 extending to near the midlen'gth of the trunk, and forminga return passage which has at such point communication with averticalpassage 23, that opens into the before described verticalconduit 11 and longitudinally slitted head 12 of the exhaust ventilatingmeans of theoven,

Each trunk 21 and conduit 23 above described are located in closeproximity to a heating unit of the oven chamber, preferably between suchunit and an adjacent side wall of the oven structure, and as so arrangedwill receive heat from the heating unit to properly temper the airpassing through said conduit and header before the discharge of the airinto the oven chamber. In that the central conduit 19 and the pair ofhorizontal trunks associated therewith, supply air to both oven chambersat points at opposite sides of the partition 3, of the oven structure,the said conduit 19 and trunk 21 will be made of a greater size ofcapacity than the side conduits 20 and their trunks, which have theopposed relation in an oven chamber as shown in Fig. 3.

Another and material part of the invention involves means for theautomatic control of the operating motor 25 of the rotary pressureblower 18 aforesaid, so that motive power will only be supplied to saidmotor when, in the type of oven shown in the drawings, the entry andexit doors 4 and 5 are in a closed condition, and in like manner uponthe closing of a single entry and exit door of another ordinary form ofthe present type of ovens. With the oven chambers filled with thearticles to be dried or enameled, the heating means started, and theaforesaid oven doors or door closed, motive power will be automaticallyturned on the motor 25, to bring the pressure blower into action andobtain the added and forced ventilation of the present invention in theinitial drying or enameling operation of the oven. Another material partof the invention involves the inclusion of an automatic time switch inthe operating electric line or circuit 25 of the motor 25 of thepressure blower 18 aforesaid, and so that the supply of electro-motiveshut off by the action of the automatic time switch when a predeterminedperiod of time has elapsed after a starting of the oven operation.

The preferred construction and arrangement of parts and means forattaining the automatic control of the motor 25 above described consistsas follows:

-An electric starter mechansim of any usual and suitable construction,usually of the three phase relay type, has connection with any usualsource of electro-motive force and is adapted to regulate and'controlthe delivery of electro-motive force to an operating electrical circuitor line 27 in which is arranged the electric motor 25 of the rotarypressure blower 18 aforesaid. In such construction the electric line 27is provided with automatic controlling means as follows:

A switch or circuit closer 28, usually of the ordinary push closingtype, and individual to each oven door 4, 5, is included in the electricline or circuit 27 with the movable member of the switch 28 arranged foroperative engagement by an oven door, to be moved to a closed conditionas said'door is moved to a like closed condition. The construction andarrangement is such that the 7 of the automatic time switch mechanism 29heretofore referred to and which is operated by any usual timingmechanism, preferably however by a train of speed reducing gearingarranged intermediate of the power shaft of the electric motor 25 of thepressure blower 18, and a shaft of said speed reducing gearing carryingthe operating cam 30 of the switch mechanism 29. In the constructionillustrated in Figs. 1 and 4, the operating cam 30, of a disk form isarranged to make a complete revolution in a period of on or about twentyminutes, and is provided with a cam projection 31 having operativeengagement with a. sliding bar 32 so as to move the same positively inone direction, against the stress of a spring 33, tending to move saidbar in the other direction.

The sliding bar32 has rigid operative connection with the movable memberof the tion in connection with the opening of the time switch 29 by thecam projection 31,

involves means for holding said switch in its the path at the timeswitch bar 32, with theends of said bars 34 abutting at a point mid waythe width of the bar 32. The respective ends of said door switch bars 34are in the form of sliding spring shoes 35 attached to the bars 34 in amanner permitting limited independent movement between a shoe and a barin a practical operation of the parts as follows:

With the oven door switches 28 in an open condition, the respectivespring shoes are in abutting contact and adapted to support and hold thetime switch bar 32 in the open condition of the time switch 29, and towhich position the bar 32 had been moved by the cam projection 31 of thecam disk 30 aforesaid. The construction of'parts, permitting thewithdrawal of the end of the time switch bar 32 from between the shoes35 and a subsequent movement of said shoes beneath the end of the bar32, to hold the tame in the position above described and maintain thetime switch 29 in an open condition, and from the relation of partsshown in Fig. 5, to that shown in Fig. 4.

With the door switches 28 moving to an open condition in an openingof-the oven doors. the spring shoes 35 associated with said do orswitches are withdrawn from beneath the end of the time switch bar 32 topermit the same to move and effect a closure of the time switch 29, butin that said time switch is in series with the open door switches, noelectric current will pass to the motor 25 of the pressure blower "18through the-supply circuit 25 aforesaid. ,With the -above describedcondition prevailing, the H emptying and refillingof the chamber of theoven is performed, and the oven doors closed. With such closure of theoven doors, the door switches 28 associated'with said doors also move to'closedcondition to complete the motive power circuit 25 and cause thepressureblower motor 25 to operate. a

With the continued operation of said motor 25. the associated timingmechanism operates in unison therewith, and at the predetermined periodof time brings the cam projection 31 into operative engagement with thetime switch bar 32 to attain an opening of the time switch 29 and astoppage of the operation of the motor and associated pressure blower18. With such movement of the time switch bar 32'its end is withdrawnfrom between the spring shoes aforesaid, and said shoes will move underthe influence of their springs beneath the end of the bar 32, to holdthe same in such position, for succeeding series of the operations firstdescribed.

In the present improvement while the oven doors areopen, their switches28 are in an open condition while the time switch 29 is in a closedcondition, and the pressure blower 18 remains inactive during the breakin the motor circuit 25 supplying its motor 25, With the oven doorsmoved to a closed condition at the beginning of the operation of theoven, the door switches 28 also move to a closed conditionto close thesupply circuit 25 of the motor 25 and cause the same to operate thepressure blower 18, to supply thebefore described added supply of air tothe oven chamber to properly ventilate the same in the initial portionof the operation of the oven. Such supply continues until the amelingoperation, as the oven doors are opened for an emptying and refilling ofthe oven chamber, the door switches 28 also move to an open conditionand in doing so withdraw the spring shoes 35 from beneath the timeswitch bar 32 to permit a movement of the sameto cause the closure ofthe time switch 29, but in that said door switches are in an opencondition, the supply circuit 25 to the motor 25 will-not be completeduntil said door switches are again closed, in the next succeedingoperation of the oven,

which started with the closing of the ovendoors and associated doorswitches 28.

Having thus fully described our invention what we claim and desire tosecure by Let ters Patent is 1. The herein described method of operating drying and enameling ovens of the exhaust ventilation type, the samecomprising the forcing of a supplemental supply of air through the ovenchamber during the initial trolling the period of such supply by atiming means, and controlling said timing means in turn by the closedand the open' condition of the oven doors.

2. In a safety operating system for dry portion of the oven operation. A

3. In a safety operating system for dr ing or enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, and a timing means controlling the operation of saidblower and confine the operation of the blower to the initial portion-ofthe oven operation, and controlling connections between the doors of theoven and said timing means. 7

4:. In a safety operating system for drying and enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted toforce a supplementary supply of air throughthe oven chamber, an electric motor operatively :onnected to saidblower, and an electric time switch mechanism controlling theoperation'of said motor.

5. In a safety operating system for drying and enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, an electric motor operatively connected to saidblower, an electric time switch mechanism controlling the operation ofsaid motor, and an electric switch individual-to and operativelyconnected to an oven door and arranged in series with said time switchmechanism in the motor supply circuit.

6. In a safety operating system for drying and enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, an electric motor operatively connected to ,saidblower, an electric time switch mechanism controlling the operation ofsaid motor'and switches "indi-' vidual to the respective oven doors andar-' ranged in series with said time switch mechanism in themotor'suppl'y circuit.

7. In a safety operating system for drying and enameling ovens of theexhaust ventilation type,.the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, a electric motor operatively portion of the operationof the oven, con-'- oven 'door and arranged in series with the timeswitch mechanism of the motor supply circuit, the time switch mechanism,including a rotary cam having operative engagement with a bar of themovable contact member of the time switch to move the same to an openposition, the movable contact member of the door switch having a barmoving in a path at right angles to the path of the bar of the movablecontact member of the time switch and having a spring shoe at its freeend adapted to engage an end of said time switch bar and hold the timingswitch in an open condition.

8. In a safety operating system for drying and enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, an electric motor operatively connected to saidblower, an electric time switch mechanism controlling the operation ofsaid motor, and an electric switch individual to and operativelyconnected to an oven door and arranged in series with the time switchmechanism of the motor supply circuit, the time switch mechanismincluding a rotary cam having operative engagement with a bar of themovable contact member of the time switch to move the same to an openposition, the movable contact member of the door switch having a barmoving in a path at right angles to the path of the bar of the movablecontact member of the time switch, a spring actuated shoe slidinglymounted on the free end of the bar of the movable contact member of thedoor switch, and means for limiting the independent movement of 'saidshoe.

9. In a safety operating system for drying and enameling ovens of theexhaust ventilation type, the combination of an oven structure, apressure blower adapted to force a supplementary supply of air throughthe oven chamber, an electric motor operatively connected to saidblower, an electric time switch mechanism controlling the operation ofsaid motor, switches individual to the ,respective oven doors andarranged in series with the said time switch in the motor supplycircuit, the time switch mechanism including a rotary cam havingoperative engagement with a bar of the movable contact member of thetime switch to move the same to its open position, the movable contactmembers of the door switches having operative connections with barssliding in a path at right angles to the aforesaid bar of the timeswitch, each door switch bar having a spring shoe at its free endadapted to engage an end of the bar of. the time switch and hold saidtime switch in an open condition. r

10. In a safety operating systemfor drying and enameling ovens, thecombination of an oven structure, anexhaust fan having duct connectionwith the top and bottom of the chamber of the oven structure, a pressure blower having duct connection with said chamber and adapted toforce a supply of air into the same, and means for confining theoperation of said blower to an initial portion of the period of the ovenoperation. I

11. In a safety operating system for drying and enameling ovens, thecombination of an oven structure, an exhaust fan having duct connectionwith the top and bottom of the chamber of the oven structure, a pressureblower having duct connection with said chamber and adapted to force asupply of air into the same, and an automatic tim ing means forconfining the operation of said blower to an initial portion of the peri0d of the oven operation. I

12. In a safety operating system for dry ing and enameling ovens, thecombination of an oven structure, an exhaust'fan having duct connectionwith the top and bottom of blower having duct connection with saidchamber and adapted to force a supply of air into the same, an automatictiming means for confining the operation of said blower to an initialportion of the period of the oven operation, and means operativelyconthe sides of the oven chamber adjacent, to

the heating units thereof and adapted to force a supply of air into saidchamber, and

means for confining the'operation of said blower to an initial portionof the period of the oven operation.

14: In a safety operating system for drying and enameling ovens, thecombination of an oven structure, an exhaust fan having duet connectionwith the top and bottom of the chamber of the oven structure, a pressureblower having connection by delivery ducts with the mid-height of thechamber of the oven structure, with said ducts arranged at the sides ofthe oven chamber adjacent to the heating units thereof and adapted toforce a supply of air unto said chamber, and an automatic timing meansfor confining the operation of said blower to an initial portion of the.period of the oven operation.

15. In a safety operating system for drying and enameling ovens, thecombination of an oven structure, an exhaust fan having duct connectionwith the; top and bottom of the chambenof the oven structure, a pressurethe chamber of the oven structure, a pressure blower having connectionby delivery duets with the mid-height of the chamber of the ovenstructure, With said dliCfiS arranged at the sides of the oven chamberadjacent to the heating units thereof and adapted to force a-supply ofair into said chamber, an automatic timing means for confining theoperation of said blower to an initial portion of the period of the ovenoperation, and means operatively connected to a door of 10 the ovenstructure for controlling the operation of said timing means.

Signed at Chicago, Illinois, July, 1926.

ARTHUR MAEIHJER. KARL SIEGELE.

